Stabilty Ball Position Paper

The Use of Stability Balls in the Workplace in Place of the Standard Office Chair

The stability ball is a large (diameter ranging from 60-100cm) inflated ball
primarily used for core stabilizing exercises such as abdominal crunches and
back extensor exercises (Vera-Garcia et al, 2000; Drake et al, 2006).
Stability balls are also often used in rehabilitation settings to aid in whole
body balance development and control. However, recently, their popularity
as an alternative to the standard office chair has risen.

Stability ball manufactures claim that using the ball in place of an office
chair has benefits such as increased trunk muscle activation and thus increased
core strength, improved posture, and decreased discomfort. The claim of
decreased discomfort is based on research that has shown a positive relationship
between reduced trunk muscle strength and individuals with low back pain (Ashmen
et al, 1996; Lee et al, 1995). However conflicting research has reported
no relationship between strength and low back pain (Biering-Sorensen,
1984). Other research, however, points to reduced trunk muscle endurance,
not strength, as being a better indicator of which individuals report low back
pain (Luoto et al, 1995).

It is well accepted that more neutral spine postures during workplace exposures
may reduce the development of low back pain (Punnett et al, 1991). These
ideas suggest that if the claims made by stability ball companies are in fact
correct, then the stability ball may have some potential to decrease and/or
prevent low back pain associated with prolonged seated work. However,
prolonged exposure to increased muscle activation may also be detrimental to
individuals, as research has shown that muscle activation with few rest breaks,
over extended periods, can result in localized muscle pain or overload (Jonsson,
1982; Veiersted et al, 1990).

Prior to the work conducted at the University of Waterloo, no study has ever
directly compared the trunk muscle activation and spine posture of individuals
while sitting on a stability ball to those on a standard office chair.
However, anecdotal evidence suggests that while initial use of a stability ball
as a chair may induce low back pain, progressive use may actually help reduce
low back symptoms after the user has accommodated to using a ball as a chair
(Merritt and Merritt, 2007). A recent study by O'Sullivan and colleagues
(2006) examined differences in trunk muscle activation and spine posture while
sitting on the SitFit', an air filled cushion that is placed on top of the users
seat pan with similar claims to stability ball manufacturers, as compared to a
standard office chair for a short five minute duration of sitting. While
they found no differences in trunk muscle activation, spinal lordosis, or pelvic
tilt, they did observe increased spinal sway while on the SitFit'; however this
may simply be participants getting settled on the device given the short
duration of the seated exposures.

The first study conducted in Dr Jack Callaghan's lab (Gregory et al, 2006)
examined trunk muscle activation patterns and lumbar spine posture in 14 healthy
men and women while sitting on a stability ball for one hour, and in a standard
office chair for one hour, presented in random order. Results showed no
significant differences between the muscle activation patterns while on the ball
versus the chair with the exception of the left thoracic erector spinae muscle,
which could be attributed to handedness and workplace interaction while sitting
on different surfaces. Further, increased discomfort in both the low back
and buttocks region was reported by all individuals while sitting on the ball as
compared to the chair. A similar study conducted in Dr Stuart McGill's lab
(McGill et al, 2006) further examined muscular activation patterns and lumbar
spine posture while sitting on a stability ball, but compared it to sitting on a
standard wooden stool. This study also found no significant differences
in muscle activation and lumbar spine posture. Further, this study had the
added advantage of the quantification of low back compression and spine
stability while sitting on the two surfaces but found no differences in the
magnitude of these measures between the ball and stool. Both these studies
employed individuals who were not habitual users of balls as office chairs and
no accommodation training was provided.

Given the results of the work conduced at Waterloo, it appears as though there
are no benefits to sitting on a stability ball as compared to a standard office
chair and claims made by stability ball manufactures, as stated above, were
disproved by the current work. Over a prolonged period of sitting (one
hour) no differences in trunk muscle activation patterns were observed,
suggesting the ball does not aid in core strengthening, and no differences were
found in lumbar spine posture, suggesting that the ball does not actually invoke
an improved posture. Moreover, the most important finding of these
studies was that individuals actually complained of more discomfort when sitting
on the stability ball - disproving the final claim made by manufactures.

Therefore, it is of the authors' opinions that stability balls should not used
as an alternative to the standard office chair since the device itself, in the
absence of other physical training and workstation interventions, does not seem
to provide any inherent benefits to the end user. Further, using the
stability ball as a chair may actually increase the risk of developing low back
discomfort and may increase the risk of sustaining an injury due to the inherent
unstable nature of these balls.